Characterization of a thermotolerant laccase produced by Streptomyces sp. SB086

Laccases have become desirable enzymes for application in many industrial processes. Nowadays, most of these enzymes are obtained from fungi. Among prospective studies for bacterial laccase genes, some have included actinomycetes, but only a few studies have characterized the enzyme produced. Thus, we have isolated a laccase-producing actinomycete from forest soil under restoration process and further aimed to characterize its produced enzyme. The isolate SB086 was assigned to the Streptomyces genus by a combination of phenotypical, chemical and phylogenetic properties. Our data indicate that the bacterium produces a thermotolerant laccase. The maximum activity was obtained in the pH range 4.0–5.0 and at 50 °C in reaction mixture containing 5 mM CuSO₄; thermal stability was noted at 60 °C and 70 °C—a well-desired characteristic for industry. The active enzyme presented a high molecular mass (over 100 kDa) and was less sensitive to inhibition by metal ions than generally described for bacterial laccases. Our findings support in silico data of bacterial laccase secretion, and reinforce the view that actinomycetes may be a rich source of laccase for industrial application.